Method for the low-temperature separation of air and air separation plant

Abstract

A method for the low-temperature separation of air using an air separation plant which comprises a rectification column arrangement ( 10 ) having a pressure column, a low-pressure column and an argon column, wherein: the low-pressure column comprises a first and a second rectification region (A, B); the argon column comprises a first and a second rectification region (C, D, D 1 , D 2 ); argon-enriched fluid is removed from the low-pressure column between the first and second rectification region (A, B) thereof and is fed into the first rectification region (C) of the argon column; and argon-depleted fluid is removed from the first rectification region (C) of the argon column ( 13 a, 13 b ) and is fed into the low-pressure column between the first and second rectification region (A, B) thereof.

1 . A method for the low-temperature separation of air using an air separation plant which comprises a rectification column arrangement having a pressure column, a low-pressure column and an argon column, wherein:
 the low-pressure column is designed in one or more parts and comprises a first and a second rectification region (A, B), and the argon column is designed in one or more parts and comprises a first and a second rectification region (C, D, D 1 , D 2 ),   between the first and second rectification regions (A, B) of the low-pressure column, a first transfer fluid enriched in argon is removed from the low-pressure column and fed into the argon column in a first transfer quantity below the first rectification region (C) of the argon column,   below the first rectification region (C) of the argon column, a second transfer fluid depleted of argon is removed from the argon column and fed into the low-pressure column in a second transfer quantity between the first and second rectification regions (A, B) of the low-pressure column,   wherein   the air separation plant is operated in a first operating mode and in a second operating mode,   a nitrogen product is discharged from the air separation plant in the first operating mode in a larger product quantity than in the second operating mode,   a pressure is set in the argon column in a pressure range that in the first operating mode   corresponds to a pressure range in which the low-pressure column is operated, or   a pressure range that is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar lower,   and which in the second operating mode is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar below the pressure range of the argon column in the first operating mode,   and in that the rectification column arrangement comprises a pure oxygen column in which a pressure is adjusted in a pressure range that in the first operating mode   corresponds to the pressure range in which the low-pressure column is operated, or   a pressure range that is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar lower,   and which in the second operating mode is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar below the pressure range of the pure oxygen column in the first operating mode, wherein the pure oxygen column is operated with a liquid as the return flow, which is removed from the argon column between the first and second rectification regions (C, D) of the argon column, and wherein a head gas is removed from the pure oxygen column and fed into the argon column between the first and second rectification regions (C, D, D 1 , D 2 ) of the argon column.   
     
     
         2 . The method according to  claim 1 , wherein a valve that is provided in a line for feeding the first transfer quantity into the argon column is closed in the second operation mode, or more tightly in the second operation mode than in the first operation mode. 
     
     
         3 . The method according to  claim 1 , in which the pressure column and the low-pressure column are connected in a heat-exchanging manner by means of a main condenser, wherein a recirculating stream is formed using head gas from the low-pressure column, which is heated, compressed, cooled again, passed partially or completely through the main condenser and/or partially or completely through a sump evaporator of the pure oxygen column, condensed there at least partially, and fed back into the pressure column and/or the low-pressure column. 
     
     
         4 . The method according to  claim 1 , wherein a product quantity of the nitrogen product that is discharged from the air separation plant in the second operation mode is at least 2.5% less, at least 10% less, or 10% to 60% less than in the first operation mode. 
     
     
         5 . The method according to  claim 1 , wherein, between the first and the second operating mode, the pressure in the low-pressure column is changed by not more than 100 mbar. 
     
     
         6 . The method according to  claim 1 , with which the first rectification region (A) and the second rectification region (B) of the low-pressure column are accommodated in a common column shell in which the second rectification region (B) of the low-pressure column is arranged above the first rectification region (A) of the low-pressure column. 
     
     
         7 . The method according to  claim 1 , with which the first and second rectification regions (C, D) of the argon column are accommodated in separate column shells, and with which the column shell, in which the first rectification region (C) of the argon column is accommodated, is arranged in particular above a column shell of the pure oxygen column and is connected thereto or is designed integrally therewith. 
     
     
         8 . The method according to  claim 1 , wherein the first rectification region (A) of the low-pressure column is accommodated in a first column shell, the second rectification region (B) of the low-pressure column is accommodated in a second column shell, and the first and second column shells are arranged next to one another. 
     
     
         9 . The method according to  claim 8 , with which the first column shell and a column shell of the pressure column are arranged one above the other and are designed in the form of a double column. 
     
     
         10 . The method according to  claim 8 , with which the second rectification region (D) of the argon column is subdivided into a first subregion (D 1 ) and a second subregion (D 2 ), wherein the first rectification region (C) of the argon column is accommodated in a third column shell, the first subregion (D 1 ) of the second rectification region (D) of the argon column is accommodated above the first rectification region (C) of the argon column in the third column shell, and the second subregion (D 1 ) of the second rectification region (D) of the argon column is accommodated in the fourth column shell. 
     
     
         11 . The method according to  claim 10 , with which gas above the first rectification region (A) of the low-pressure column is withdrawn from the first column shell and fed into the second column shell in a first portion below the second rectification region (B) of the low-pressure column and into the third column shell as the first transfer fluid in a second portion below the first rectification region (C) of the argon column, with which liquid is withdrawn from the third column shell below the first rectification region (C) of the argon column and is fed into the first column shell as the second transfer fluid above the first rectification region (A) of the low-pressure column, and with which liquid is withdrawn from the second column shell below the second rectification region (B) of the low-pressure column and is fed into the third column shell below the first rectification region (C) of the argon column. 
     
     
         12 . The method according to  claim 11 , with which a lower end of the second column shell lies geodesically above an inlet position of the first transfer fluid into the third column shell, the first transfer fluid is transferred purely into the third column shell. 
     
     
         13 . The method according to  claim 1 , with which the pressure column is operated at a pressure in an operating pressure range of 9 to 14.5 bar, and with which the low-pressure column is operated at a pressure in an operating pressure range of 2 to 5 bar. 
     
     
         14 . An air separation plant which comprises a rectification column arrangement having a pressure column, a low-pressure column and an argon column, wherein:
 the low-pressure column is designed in one or more parts and comprises a first and a second rectification region (A, B), and the argon column is designed in one or more parts and comprises a first and a second rectification region (C, D, D 1 , D 2 ), and   the air separation plant is configured such that   between the first and second rectification regions (A, B) of the low-pressure column, a first transfer fluid enriched in argon is to be removed from the low-pressure column and is to be fed into the argon column in a first transfer quantity below the first rectification region (C) of the argon column,   below the first rectification region (C) of the argon column, a second transfer fluid depleted of argon is to be removed from the argon column and is to be fed into the low-pressure column in a second transfer quantity between the first and second rectification regions (A, B) of the low-pressure column,   wherein   is configured for operation in a first operating mode and in a second operating mode, wherein:   the air separation plant is configured to discharge a nitrogen product from the air separation plant in the first operating mode in a larger product quantity than in the second operating mode, and   the air separation plant is configured to adjust a pressure in the argon column in a pressure range that, in the first operating mode,   corresponds to a pressure range in which the low-pressure column is operated, or   a pressure range that is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar lower,   and which in the second operating mode is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar below the pressure range of the argon column in the first operating mode,   and in that the rectification column arrangement comprises a pure oxygen column, wherein the air separation plant is configured to adjust a pressure in the pure oxygen column in a pressure range that, in the first operating mode,   corresponds to the pressure range in which the low-pressure column is operated, or   a pressure range that is at least 50 mbar, at least 100 mbar and/or up to 700 mbar or 900 mbar lower,   
       and which in the second operating mode is at least 100 mbar and/or up to 700 mbar or 900 mbar below the pressure range of the pure oxygen column ( 14 ) in the first operating mode, wherein the air separation plant is configured for the pure oxygen column to be operated with a liquid as the return flow, which is removed from the argon column between the first and second rectification regions of the argon column, and wherein the pure oxygen column comprises means for removing a head gas that is fed into the argon column between the first and second rectification regions of the argon column.